鄂尔多斯盆地周家湾长6和长8油层组成藏控制因素

摘要

The pool-forming model and controlling factors of Chang-6 and Chang-8 oil-bearing layers of Triassic Yanchang Formation in Zhoujiawan area of Ordos Basin were investigated by analyzing the influence of generation and expulsion of hydrocarbon of source rock on hydrocarbon accumulation. Also,the differences of deposition and diagenesis of reservoir,and the differences of pool-forming process were studied and summarized.It shows that the large scale oil source rock of Chang-7 supplied the oil source and driving force,the connectivity of sand bodies and structure fractures supplied the migration passageway for the oil and gas,the large scale overriding sand bodies played a role in the formation of favorable reservoir rock, the difference of deposition and diagenesis leaded to the formation of relative high porosity and permeability reservoir and controlled the enrichment area of oil pool.It revealed that the oil from the Chang-7 oil source rock firstly migrated upward to the Chang-6 reservoir,then migrated horizontally through the connective sand bodies to the place far away from Chang-7 oil source rock,forming large scale oil pool along the north-east direction sand bodies.For the oil pools of Chang-8 ,the oil from the Chang-7 oil source rock mainly migrated downward to Chang-8 ,but the scale of second horizontal migration was limited and therefore,the area of oil pool of Chang-8 was small.%探讨鄂尔多斯盆地周家湾地区三叠系延长组长6、长8层成藏主控因素及成藏模式。从长7烃源岩生排烃影响原油运聚及长6、长8沉积、成岩的差异性研究入手，总结成藏差异。结果表明，长7大面积分布的烃源岩为成藏提供了物质基础和运移动力；该区发育的长6、长8连通性砂体和构造裂缝提供了运移输导条件；长6、长8大规模叠置砂体形成了良好的储集体；沉积、成岩差异形成的相对高孔高渗储层发育区控制着油藏富集区的分布。长6层成藏模式表现为长7油源先向上运移至长6成藏，而后侧向沿连通砂体继续运聚成藏，直至扩展到远离长7烃源岩分布区，形成沿北东向砂体大面积展布的油藏；长8层成藏模式则主要为长7烃源岩向下运聚成藏，二次侧向运移较少，油藏面积较小。